The present invention relates to a chemical mechanical polishing carrier head that includes a resistive heating system, and associated methods.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, it is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the exposed surface of the substrate becomes increasingly nonplanar. This nonplanar surface presents problems in the photolithographic steps of the integrated circuit fabrication process. Therefore, there is a need to periodically planarize the substrate surface.
One accepted method of planarization is chemical mechanical polishing (CMP). This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is placed against a moving polishing surface, such as a rotating polishing pad. The polishing pad can be a “standard” polishing pad with a durable roughened surface or a “fixed-abrasive” polishing pad with abrasive particles held in a containment media. The carrier head provides a controllable load to the substrate to push it against the polishing pad. A polishing slurry, which can include abrasive particles, is supplied to the surface of the polishing pad.
The polishing rate in a chemical-mechanical process depends on a variety of factors, including the pressure between the substrate and the polishing pad and the temperature at the polishing surface. Consequently, differences in pressure or temperature across the surface of the substrate during polishing can cause the polishing rate to vary from one section of the substrate surface to another.